AceShowbiz -

Dr. Addison Montgomery is getting married, soon. The character's star Kate Walsh is planning to tie the knot with fiance Alex Young over America's Labor Day weekend, September 3rd later this year.

Walsh and Young became engaged after the 20th Century Fox production co-president proposed in San Fransisco and presented her with Neil Lane Jubilee-cut diamond back on May 15th.

And now the couple is planning to have a three-day wedding celebration set to take place at Southern California's Ojai Valley Inn & Spa with 110 guests invited. They will list help from wedding planner Jo Gartin and her company Love Luck and Angels.

People quoted a source as saying, the "festivities will kick off with a rehearsal dinner on Friday, include a pre-wedding meal on Saturday and a sunset ceremony, then wrap up with a post-wedding brunch on Sunday." As of the Saturday event, it will be held "outdoors at the inn's Casa Elar, a Spanish-style estate."

Bride-to-be Walsh is said to wear a custom made Monique Lhuillier wedding dress. Among the celebrity guests are Walsh "Grey Anatomy"'s costars Katherine Heigl and Sara Ramirez.